Numerical and experimental investigations of oblique boundary layer transition

1999 ◽  
Vol 393 ◽  
pp. 23-57 ◽  
Author(s):  
STELLAN BERLIN ◽  
MARKUS WIEGEL ◽  
DAN S. HENNINGSON
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Layer Transition ◽  
Oblique Waves ◽  
Starting Point ◽  
Incompressible Boundary ◽  
Tollmien Schlichting ◽  
Streamwise Streaks

A transition scenario initiated by two oblique waves is studied in an incompressible boundary layer. Hot-wire measurements and flow visualizations from the first boundary layer experiment on this scenario are reported. The experimental results are compared with spatial direct numerical simulations and good qualitative agreement is found. Also, quantitative agreement is found when the experimental device for disturbance generation is closely modelled in the simulations and pressure gradient effects taken into account. The oblique waves are found to interact nonlinearly to force streamwise vortices. The vortices in turn produce growing streamwise streaks by non-modal linear growth mechanisms. This has previously been observed in channel flows and calculations of both compressible and incompressible boundary layers. The flow structures observed at the late stage of oblique transition have many similarities to the corresponding ones of K- and H-type transition, for which two-dimensional Tollmien–Schlichting waves are the starting point. However, two-dimensional Tollmien–Schlichting waves are usually not initiated or observed in oblique transition and consequently the similarities are due to the oblique waves and streamwise streaks appearing in all three scenarios.

Numerical simulation of boundary-layer transition and transition control

1989 ◽  
Vol 199 ◽  
pp. 403-440 ◽  
Author(s):  
E. Laurien ◽  
L. Kleiser
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Transition Process ◽  
Numerical Results ◽  
Boundary Layer Transition ◽  
Two Dimensional ◽  
Layer Transition ◽  
Longitudinal Vortices ◽  
Tollmien Schlichting

The laminar-turbulent transition process in a parallel boundary-layer with Blasius profile is simulated by numerical integration of the three-dimensional incompressible Navier-Stokes equations using a spectral method. The model of spatially periodic disturbances developing in time is used. Both the classical Klebanoff-type and the subharmonic type of transition are simulated. Maps of the three-dimensional velocity and vorticity fields and visualizations by integrated fluid markers are obtained. The numerical results are compared with experimental measurements and flow visualizations by other authors. Good qualitative and quantitative agreement is found at corresponding stages of development up to the one-spike stage. After the appearance of two-dimensional Tollmien-Schlichting waves of sufficiently large amplitude an increasing three-dimensionality is observed. In particular, a peak-valley structure of the velocity fluctuations, mean longitudinal vortices and sharp spike-like instantaneous velocity signals are formed. The flow field is dominated by a three-dimensional horseshoe vortex system connected with free high-shear layers. Visualizations by time-lines show the formation of A-structures. Our numerical results connect various observations obtained with different experimental techniques. The initial three-dimensional steps of the transition process are consistent with the linear theory of secondary instability. In the later stages nonlinear interactions of the disturbance modes and the production of higher harmonics are essential.We also study the control of transition by local two-dimensional suction and blowing at the wall. It is shown that transition can be delayed or accelerated by superposing disturbances which are out of phase or in phase with oncoming Tollmien-Schlichting instability waves, respectively. Control is only effective if applied at an early, two-dimensional stage of transition. Mean longitudinal vortices remain even after successful control of the fluctuations.

The control of boundary-layer transition using a wave-superposition principle

1983 ◽  
Vol 137 ◽  
pp. 233-250 ◽  
Author(s):  
Andrew S. W. Thomas
Keyword(s):  
Boundary Layer ◽  
Superposition Principle ◽  
Three Dimensional ◽  
Feedback System ◽  
Boundary Layer Transition ◽  
Single Frequency ◽  
Two Dimensional ◽  
Layer Transition ◽  
Tollmien Schlichting ◽  
Equal Amplitude

An experimental study has been made of the concept of controlling boundary-layer transition by superimposing in the flow Tollmien–Schlichting waves that are of equal amplitude and antiphased to the disturbances that grow and lead to transition. The cases that have been considered are transition arising from a single-frequency two-dimensional disturbance and transition arising from a nonlinear interaction between two waves of different frequency. A feedback system for controlling transition has also been studied. In each case, both hot-wire surveys and flow visualization have shown that it is possible to delay transition but that the flow cannot be restored completely to its undisturbed state. This appears to be a consequence of interactions between the very weak three-dimensional background disturbances in the flow and the primary two-dimensional waves. The implications of these findings in an implementation of the concept are discussed.

Weakly nonlinear stages of boundary-layer transition initiated by modulated Tollmien–Schlichting waves

2013 ◽  
Vol 732 ◽  
pp. 571-615 ◽  
Author(s):  
I. B. de Paula ◽  
W. Würz ◽  
E. Krämer ◽  
V. I. Borodulin ◽  
Y. S. Kachanov
Keyword(s):  
Boundary Layer ◽  
Modulation Frequency ◽  
Low Frequency ◽  
Natural Disturbance ◽  
Boundary Layer Transition ◽  
Two Dimensional ◽  
Layer Transition ◽  
Weakly Nonlinear ◽  
Resonant Interactions ◽  
Tollmien Schlichting

AbstractWeakly nonlinear interactions involving amplitude-modulated Tollmien–Schlichting waves in an incompressible, two-dimensional aerofoil boundary layer are investigated experimentally. Selected resonant regimes are examined with emphasis on the regimes where more than one fundamental Tollmien–Schlichting (TS) wave is present in the flow. The experiments were performed on an NLF-type aerofoil section for glider applications. Disturbances with controlled frequency-spanwise-wavenumber spectra were excited in the boundary layer and studied by phase-locked hot-wire measurements. The results show that nonlinear mechanisms connected with the steepening of the primary TS wave modulation do not play any significant role in the transition scenarios studied. It is also shown that modulations of the two-dimensional fundamental waves tend to generate additional modes at modulation frequency. These low-frequency disturbances are found to be produced by a non-resonant quadratic combination of spectral components of the primary, modulated TS wave. The investigations show that the efficiency of the process is higher for three-dimensional low-frequency modes in comparison with two-dimensional modes. Thus, the emergence of three-dimensionality for the low-frequency waves does not require any resonant interactions. In a subsequent nonlinear stage, the self-generated detuned subharmonics are found to be strongly amplified due to resonant interactions with the primary TS waves. The sequence of weakly nonlinear mechanisms found and investigated here seems to be the most likely route to the laminar–turbulent transition, at least for two-dimensional boundary layers of aerofoils with a long extent of laminar flow and in a ‘natural’ disturbance environment.

Effects of Weak Free Stream Nonuniformity on Boundary Layer Transition (Keynote Paper)

2003 ◽  
Author(s):  
Jonathan H. Watmuff
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Mean Flow ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Tollmien Schlichting ◽  
Distorted Waves ◽  
Thickness Variations

Experiments are described in which well-defined FSN (Free Stream Nonuniformity) distributions are introduced by placing fine wires upstream of the leading edge of a flat plate. Large amplitude spanwise thickness variations are present in the downstream boundary layer resulting from the interaction of the laminar wakes with the leading edge. Regions of elevated background unsteadiness appear on either side of the peak layer thickness, which share many of the characteristics of Klebanoff modes, observed at elevated Free Stream Turbulence (FST) levels. However, for the low background disturbance level of the free stream, the layer remains laminar to the end of the test section (Rx ≈ l.4×106) and there is no evidence of bursting or other phenomena associated with breakdown to turbulence. A vibrating ribbon apparatus is used to demonstrate that the deformation of the mean flow is responsible for substantial phase and amplitude distortion of Tollmien-Schlichting (TS) waves. Pseudo-flow visualization of hot-wire data shows that the breakdown of the distorted waves is more complex and occurs at a lower Reynolds number than the breakdown of the K-type secondary instability observed when the FSN is not present.

Experimental investigations on characteristics of boundary layer and control of transition on an airfoil by AC-DBD

2018 ◽  
Vol 32 (08) ◽  
pp. 1850108 ◽  
Author(s):  
Xi Geng ◽  
Zhiwei Shi ◽  
Keming Cheng ◽  
Hao Dong ◽  
Qun Zhao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Boundary Layer Transition ◽  
Plasma Actuators ◽  
Experimental Investigations ◽  
Dbd Plasma ◽  
Layer Transition ◽  
Piv Measurement ◽  
Induced Flow ◽  
And Control

Plasma-based flow control is one of the most promising techniques for aerodynamic problems, such as delaying the boundary layer transition. The boundary layer’s characteristics induced by AC-DBD plasma actuators and applied by the actuators to delay the boundary layer transition on airfoil at Ma = 0.3 were experimentally investigated. The PIV measurement was used to study the boundary layer’s characteristics induced by the plasma actuators. The measurement plane, which was parallel to the surface of the actuators and 1 mm above the surface, was involved in the test, including the perpendicular plane. The instantaneous results showed that the induced flow field consisted of many small size unsteady vortices which were eliminated by the time average. The subsequent oil-film interferometry skin friction measurement was conducted on a NASA SC(2)-0712 airfoil at Ma = 0.3. The coefficient of skin friction demonstrates that the plasma actuators successfully delay the boundary layer transition and the efficiency is better at higher driven voltage.

Criteria for Boundary Layer Transition

2011 ◽  
Author(s):  
Stefan Becker ◽  
Donald M. McEligot ◽  
Edmond Walsh ◽  
Eckart Laurien
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Boundary Layer Flow ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Turbulence Level ◽  
Two Dimensional ◽  
Freestream Turbulence ◽  
Layer Transition ◽  
Layer Flow

New results are deduced to assess the validity of proposed transition indicators when applied to situations other than boundary layers on smooth surfaces. The geometry employed utilizes a two-dimensional square rib to disrupt the boundary layer flow. The objective is to determine whether some available criteria are consistent with the present measurements of laminar recovery and transition for the flow downstream of this rib. For the present data — the proposed values of thresholds for transition in existing literature that are based on the freestream turbulence level at the leading edge are not reached in the recovering laminar run but they are not exceeded in the transitioning run either. Of the pointwise proposals examined, values of the suggested quantity were consistent for three of the criteria; that is, they were less than the threshold in laminar recovery and greater than it in the transitioning case.

Leading-edge receptivity of a hypersonic boundary layer on a flat plate

2001 ◽  
Vol 426 ◽  
pp. 73-94 ◽  
Author(s):  
A. A. MASLOV ◽  
A. N. SHIPLYUK ◽  
A. A. SIDORENKO ◽  
D. ARNAL
Keyword(s):  
Boundary Layer ◽  
Acoustic Waves ◽  
Free Stream ◽  
Three Dimensional ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Inclination Angles ◽  
Tollmien Schlichting ◽  
Radiation Conditions

Experimental investigations of the boundary layer receptivity, on the sharp leading edge of a at plate, to acoustic waves induced by two-dimensional and three- dimensional perturbers, have been performed for a free-stream Mach number M∞ = 5.92. The fields of controlled free-stream disturbances were studied. It was shown that two-dimensional and three-dimensional perturbers radiate acoustic waves and that these perturbers present a set of harmonic motionless sources and moving sources with constant amplitude. The disturbances excited in the boundary layer were measured. It was found that acoustic waves impinging on the leading edge generate Tollmien–Schlichting waves in the boundary layer. The receptivity coefficients were obtained for several radiation conditions and intensities. It was shown that there is a dependence of receptivity coefficients on the wave inclination angles.

Detailed Analysis of Experimental Investigations on Boundary Layer Transition in Wake Disturbed Flow

2006 ◽  
Author(s):  
Andrea Cattanei ◽  
Pietro Zunino ◽  
Thomas Schro¨der ◽  
Bernd Stoffel ◽  
Berthold Matyschok
Keyword(s):  
Boundary Layer ◽  
Measurement Data ◽  
Boundary Layer Transition ◽  
Data Evaluation ◽  
Experimental Investigations ◽  
Layer Transition ◽  
Disturbed Flow ◽  
Time Space ◽  
Separation Bubbles ◽  
Hot Film

In the framework of a co-operation between the University of Genoa and the Darmstadt University of Technology measurement data of a former investigation at Darmstadt, comprising measurements with surface-mounted hot-film sensors on the boundary layer transition in wake disturbed flow, were transferred to Genoa, then re-evaluated and in great detail analyzed, much further than the original data evaluation. In these experimental investigations at Darmstadt, the boundary layer transition with and without transitional separation bubbles was studied on a circular cylinder in cross flow. The comparison of hot-wire traverses with the surface-mounted hot-film distributions clearly indicated that the surface-mounted hot-film technique is a very suitable measurement technique to obtain reliable information on transition and separation phenomena with both high spatial and temporal resolution. The new data evaluation techniques applied to these data at Genoa further enhanced the insight into the details of the boundary layer transition and separation process. The surface-mounted hot-film data were evaluated by means of time-space diagrams for the first three statistical moments (mean, RMS and skewness), with which the origin and the extent of unsteady separation bubbles clearly could be seen. The results obtained from these data analyses on the one hand yield a considerable enhancement of the understanding of the periodically unsteady boundary layer transition process and on the other hand they form the basis for the application of surface-mounted hot-film sensors in more complex flow situations like e.g. in cold flow multistage turbine or compressor test rigs or even in the hostile environment of real aero engine compressors or turbines.

scholarly journals Effects of Periodic Unsteady Wake Flow and Pressure Gradient on Boundary Layer Transition Along the Concave Surface of a Curved Plate

1994 ◽  
Author(s):  
M. T. Schobeiri ◽  
R. E. Radke
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Turbulence Intensity ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Concave Surface ◽  
Experimental Investigations ◽  
Ensemble Averaging ◽  
Layer Transition ◽  
Lateral Direction

Boundary layer transition and development on a turbomachinery blade is subjected to highly periodic unsteady turbulent flow, pressure gradient in longitudinal as well as lateral direction, and surface curvature. To study the effects of periodic unsteady wakes on the concave surface of a turbine blade, a curved plate was utilized. On the concave surface of this plate, detailed experimental investigations were carried out under zero and negative pressure gradient. The measurements were performed on an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate. Boundary layer measurements using a hot-wire probe were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. As the results show, the turbulent patches generated by the wakes have different leading and trailing edge velocities and merge with the boundary layer resulting in a strong deformation and generation of a high turbulence intensity core. After the turbulent patch has totally penetrated into the boundary layer, pronounced becalmed regions were formed behind the turbulent patch and were extended far beyond the point they would occur in the corresponding undisturbed steady boundary layer.

scholarly journals A CFD-Compatible Amplification Factor Transport Equation for Oblique Tollmien-Schlichting Waves in Supersonic Boundary Layers

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
JiaKuan Xu ◽  
Lei Qiao ◽  
Junqiang Bai
Keyword(s):  
Transport Equation ◽  
Amplification Factor ◽  
Flow Instability ◽  
Supersonic Flows ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Two Dimensional ◽  
Layer Transition ◽  
Low Speed ◽  
Tollmien Schlichting

Boundary layer transition is a hot research topic in fluid mechanics and aerospace engineering. In low-speed flows, two-dimensional Tollmien-Schlichting (T-S) waves always dominate the flow instability, which has been modeled by Coder and Maughmer from 2013. However, in supersonic flows, three-dimensional oblique Tollmien-Schlichting waves become dominant in flow instability. Inspired by Coder and Maughmer’s NTS amplification factor transport equation for two-dimensional Tollmien-Schlichting waves in low-speed flows and Kroo and Sturdza’s linear stability theory (LST) analysis results for oblique Tollmien-Schlichting waves in supersonic flows, a new amplification factor transport equation for oblique Tollmien-Schlichting waves has been developed based on LST. The compressible Falkner-Skan similarity equations are introduced to build the relationships between nonlocal variables and local variables so that all the variables used in the present model can be calculated using local variables. Applications of this new transport equation to the flows over supersonic flat plate, 3% thick biconvex airfoil, and one modified supersonic laminar airfoil show promising results compared with the standard LST analysis results.

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